Aircraft landing gear assembly

ABSTRACT

An aircraft landing gear assembly having a reinstating geometry in which a lock link can be moved to assume a first locking condition to inhibit movement of a stay when a main strut is in a deployed condition and a second locking condition to inhibit movement of the main strut when in a stowed condition. An unlock actuator is coupled between a first element of the stay and the lock link such that the actuator can break the lock link from the first locking condition and force it to assume the second locking condition by operational force in a single direction.

This application is a continuation of U.S. application Ser. No.16/580,118, filed on Sep. 24, 2019, which claims the benefit of andpriority to European Patent Application No. EP18196956.9, filed on Sep.26, 2018, both of which are incorporated herein by reference.

BACKGROUND

An aircraft landing gear assembly generally includes a main load bearingstrut arranged to be pivotally coupled to an aircraft so that it can bestowed within the aircraft for flight, and deployed from the aircraftfor take-off, landing, and supporting the weight of the aircraft whileit is on the ground.

A retraction actuator is generally provided to move the main strutbetween the deployed and stowed conditions. It is common for theretraction actuator to have one end arranged to be pivotally coupled tothe aircraft.

It is known for an aircraft landing gear assembly to be provided withone or more stays each having a locking condition in which it isarranged to hold the main strut in the deployed condition. It is commonfor stays to have one end arranged to be pivotally coupled to theaircraft for load reaction purposes.

Each stay can in turn be held in the locking condition by a lock link,each lock link having a locking condition in which it holds a respectivestay in the locking condition.

Each lock link can be provided with an unlock actuator arranged to moveit from the locking condition to a passive condition in which the staycan be folded from the locking condition to a passive condition, toallow the main strut to be moved to the stowed condition by theretraction actuator.

It is known for an aircraft landing gear assembly to be provided with anup-lock having a locking condition in which the main strut is held inthe stowed condition within the aircraft. It is common for an up-lock tobe movably coupled to the aircraft.

A known subclass of aircraft landing gear assembly has a “reinstating”,“re-erecting” or “self-resurrecting” geometry in which the lock link isarranged such that it can be placed in the locking condition when thelanding gear assembly is deployed and also placed in the lockingcondition when the landing gear assembly is stowed.

The lock link can be anchored to the aircraft or alternatively anotherpart of the landing gear assembly. The latter arrangement is preferablesince it avoids an additional attachment point or “hard point” on theaircraft.

This type of reinstating landing gear assembly advantageously avoids theneed for an up lock and hard points on the aircraft for the lock linkanchor. However, the present inventor has identified two problems withsuch an arrangement, as set out below.

Firstly, in order to avoid the use of sequential control during movementof the main strut from one condition to the other, it is preferred thatthe unlock actuator applies load in one direction through one movementphase of the main strut and applies load in the opposite directionthrough the opposite movement phase. For example, the unlock actuatormay be required to shorten to unlock from the deployed condition andextend to unlock in the stowed condition. However, the unlock actuatoris also required to force the lock link to assume the locked conditionin the up lock situation where the main strut is in the stowedcondition. When attached to the main strut the lock link and staymember, to which the lock link is attached, will be in the same relativeposition when the main strut is deployed and stowed, hence requiringload reversal of the unlock actuator to unlock and relock if the unlockactuator is mounted in a common position between two of these parts. Asolution is to attach one end of the unlock actuator to the aircraft,but this requires a further hard point.

Secondly, there is a certain amount of energy required to unlock thelock link due to the fact that when in the locking condition a lock linkis generally sprung into a generally aligned, over-centre position. Inthe event of a malfunction, such as a loss of the primary supply ofhydraulic pressure, the unlock actuator would not be able to release thelanding gear allowing it to fall into the down position. Consequently itis beneficial to add a second actuation means to release the gear fromthe retracted position. This may take the form of a ‘kicker’ actuator.It is however desirable to locate the kicker actuator such thatinadvertent operation does not release the lock link when in thedeployed locking condition. As such, it is known to mount the kickeractuator on the aircraft, thus requiring a further hard point.

The present inventor has devised a simplified reinstating landing gearassembly in comparison to known assemblies.

SUMMARY

By way of an overview, embodiments of the invention provide an aircraftlanding gear assembly having a reinstating geometry in which a lock linkcan be moved to assume a first locking condition to inhibit movement ofa stay when a main strut is in a deployed condition and a second lockingcondition to inhibit movement of the main strut when in a stowedcondition. An unlock actuator is coupled between a first element of thestay and the lock link such that the actuator can break the lock linkfrom the first locking condition and force it to assume the secondlocking condition by operational force in a single direction.Alternatively or in addition, an auxiliary unlock actuator can bemounted on the first element of the stay to face the lock link when themain strut is in a stowed condition.

In accordance with a first aspect of the present invention, there isprovided an aircraft landing gear assembly comprising: a main loadbearing strut, a stay and a lock link. The main load bearing strut has afirst end arranged to be movably coupled to an aircraft for the strut tobe moved between a stowed condition for flight and a deployed conditionfor take-off and landing, and a second end arranged to define or becoupled to a ground contacting assembly. The stay comprises a first stayelement having a first end pivotally coupled to a first end of a secondstay element to define a stay apex joint, a second end of the first stayelement being arranged to be pivotally coupled to the aircraft and asecond end of the second stay element being arranged to be pivotallycoupled to the strut such that the stay can be folded and unfoldedbetween: a locking condition in which the stay inhibits movement of thestrut from the deployed condition to the stowed condition; and a passivecondition in which the stay permits movement of the strut from thedeployed condition to the stowed condition. The lock link comprises afirst link element having a first end pivotally coupled to a first endof a second link element to define a lock link apex joint, a second endof the first link element being pivotally coupled to the strut at afirst location which is closer to the first end of the strut than thesecond end, and a second end of the second link element being coupled tothe stay at or adjacent to the stay apex joint such that the lock linkcan be folded and unfolded between: a first locking condition in whichthe lock link inhibits movement of the stay from the locking conditionto the passive condition; a passive condition in which the lock linkpermits movement of the stay from the locking condition to the passivecondition; and a second locking condition in which the lock linkinhibits movement of the strut from the stowed condition towards thedeployed condition, the passive condition lying between the first andsecond locking conditions as the strut moves between the deployedcondition and stowed condition. The assembly also has an unlock actuatorhaving a first end pivotally coupled to the first stay element at afirst actuator pivot point and a second end pivotally coupled to thelock link at a second actuator pivot point such that the actuator canmove the lock link from the first locking condition to the passivecondition by one of extending or retracting and that the actuator canmove the lock link from the passive condition to the second lockingcondition by the same one of extending or retracting.

Thus, an aircraft landing gear assembly according to the first aspect ofthe invention includes an unlock actuator that is anchored to the upperstay element. The present inventor has found that this results in areinstating geometry in which the unlock actuator can apply load in onedirection only to unlock the lock link from the deployed strut conditionand then lock it again in the stowed gear condition, thus avoiding theneed for sequential control during movement of the main strut from onecondition to the other.

The landing gear assembly can be arranged such that the unlock actuatorcan move the lock link from the second locking condition to the passivecondition by the opposite one of extending or retracting.

The first end of the unlock actuator can be coupled to the first stayelement at a location which is closer to the stay apex joint than thesecond end of the first stay element. This can result in an arrangementin which operational travel of the unlock actuator can be reduced incomparison to some embodiments.

The second end of the unlock actuator can be pivotally coupled to thesecond link of the lock link. This can result in an arrangement in whichoperational travel of the unlock actuator can be reduced in comparisonto some embodiments.

The aircraft landing gear assembly can further comprise an auxiliaryunlock actuator including an end effector, and being operable to movethe end effector along an actuation path between a first extension stateand a second extension state, the auxiliary unlock actuator beingeither: mounted on the stay and arranged such that when the lock link isin the second locking condition the lock link intersects the actuationpath but when the lock link is in the first locking condition the locklink does not intersect the actuation path, such that movement of theend effector from the first extension state to the second extensionstate unlocks the lock link by contacting the lock link when the locklink is in the second locking condition, but movement of the endeffector from the first extension state to the second extension statedoes not unlock the lock link when the lock link is in the first lockingcondition; or mounted on the lock link and arranged such that when thelock link is in the second locking condition the stay intersects theactuation path, but when the lock link is in the first locking conditionthe stay does not intersect the actuation path such that movement of theend effector from the first extension state to the second extensionstate unlocks the lock link by contacting the stay when the lock link isin the second locking condition but movement of the end effector fromthe first extension state to the second extension state does not unlockthe lock link when the lock link is in the first locking condition. Thiscan result in an arrangement in which the size and/or weight of theunlock actuator can be reduced and/or improved reliability of unlockingof the lock link from the second locking condition in comparison to someembodiments without requiring a further hard point on the aircraft.

The aircraft landing gear assembly can further comprise a retractionactuator operable to change in length between a first extension stateand a second extension state, the retraction actuator being coupled tothe main strut such that movement of the retraction actuator from thefirst extension state to the second extension state causes the mainstrut to move from the deployed condition to the stowed condition.

The retraction actuator can be distinct from the unlock actuator.

The unlock actuator can comprise a linear actuator, and/or the auxiliaryunlock actuator comprises a linear actuator, and/or the retractionactuator comprises a linear actuator.

In accordance with a second aspect of the present invention, there isprovided an aircraft landing gear assembly comprising main load bearingstrut, a stay and a lock link. The main load bearing strut has a firstend arranged to be movably coupled to an aircraft for the strut to bemoved between a stowed condition for flight and a deployed condition fortake-off and landing, and a second end arranged to define or be coupledto a ground contacting assembly. The stay comprises a first stay elementhaving a first end pivotally coupled to a first end of a second stayelement to define a stay apex joint, a second end of the first stayelement being arranged to be pivotally coupled to the aircraft and asecond end of the second stay element being arranged to be pivotallycoupled to the strut such that the stay can be folded and unfoldedbetween: a locking condition in which the stay inhibits movement of thestrut from the deployed condition to the stowed condition; and a passivecondition in which the stay permits movement of the strut from thedeployed condition to the stowed condition. The lock link comprises afirst link element having a first end pivotally coupled to a first endof a second link element to define a lock link apex joint, a second endof the first link element being pivotally coupled to the strut at afirst location which is closer to the first end of the strut than thesecond end, and a second end of the second link element being coupled tothe stay at, or adjacent to, the stay apex joint such that the lock linkcan be folded and unfolded between: a first locking condition in whichthe lock link inhibits movement of the stay from the locking conditionto the passive condition; a passive condition in which the lock linkpermits movement of the stay from the locking condition to the passivecondition; and a second locking condition in which the lock linkinhibits movement of the strut from the stowed condition towards thedeployed condition, the passive condition lying between the first andsecond locking conditions as the strut moves between the deployedcondition and stowed condition. The assembly includes an auxiliaryunlock actuator including an end effector and being operable to move theend effector along an actuation path between a first extension state anda second extension state, the auxiliary unlock actuator being either:mounted on the stay and arranged such that when the lock link is in thesecond locking condition the lock link intersects the actuation path,but when the lock link is in the first locking condition the lock linkdoes not intersect the actuation path such that movement of the endeffector from the first extension state to the second extension stateunlocks the lock link by contacting the lock link when the lock link isin the second locking condition, but movement of the end effector fromthe first extension state to the second extension state does not unlockthe lock link when the lock link is in the first locking condition; ormounted on the lock link and arranged such that when the lock link is inthe second locking condition the stay intersects the actuation path, butwhen the lock link is in the first locking condition the stay does notintersect the actuation path such that movement of the end effector fromthe first extension state to the second extension state unlocks the locklink by contacting the stay when the lock link is in the second lockingcondition, but movement of the end effector from the first extensionstate to the second extension state does not unlock the lock link whenthe lock link is in the first locking condition.

Thus, the landing gear assembly according to the second aspect isprovided with an auxiliary unlock actuator that does not require adedicated hard point on the airframe and is arranged such thatinadvertent operation of the auxiliary unlock actuator will not unlockthe gear when in the deployed condition. This can result in anarrangement in which the size and/or weight of the unlock actuator canbe reduced and/or improved reliability of unlocking of the lock linkfrom the second locking condition in comparison to some arrangements,without requiring a further hard point on the aircraft.

The auxiliary unlock actuator can be coupled to the stay; for example,the first stay element.

The auxiliary unlock actuator can be rigidly coupled to the stay or locklink such that movement of the stay causes direct corresponding movementof the auxiliary unlock actuator. The actuator can for example becoupled by a mechanical fixing, such as one or more nut and boltarrangements, to a mounting lug on the stay or lock link.

The auxiliary unlock actuator can comprise a linear actuator and becoupled to the first stay element in an orientation such that theactuation path of the end effector is generally parallel with respect tothe longitudinal axis of the first stay element, or generallyperpendicular to the contacting surface of the lock link

Alternatively, the auxiliary unlock actuator can be pivotally coupled tothe first stay element and pivotally coupled to a leg, the leg beingpivotally coupled to the stay and defining the end effector.

The auxiliary unlock actuator can be powered by a different power sourcethan the unlock actuator, such as different hydraulic or electricalsupplies.

Optional features of the first aspect can be applied to the secondaspect and vice versa.

In accordance with a third aspect of the invention, there is provided aaircraft including one or more aircraft landing gear assembliesaccording to the first and/or second aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, certain embodiments of the invention will now bedescribed by reference to the accompanying drawings, in which;

FIG. 1 is a diagram of an aircraft landing gear assembly according to anembodiment of the invention in a deployed condition with the stay andlock link in locking conditions;

FIG. 2 is a diagram of the landing gear assembly of FIG. 1 with the locklink in the passive condition;

FIG. 3 is a diagram of the landing gear assembly of FIG. 1 with the locklink and the stay in the passive condition;

FIG. 4 is a diagram of the landing gear assembly of FIG. 1 with the locklink in the second locking condition and the stay in the passivecondition;

FIG. 5 is a diagram of the landing gear assembly of FIG. 1, showing theauxiliary unlock actuator when the gear is deployed;

FIG. 6 is a diagram of the landing gear assembly of FIG. 1, showing theauxiliary unlock actuator when the gear is stowed;

FIG. 7 is a diagram of an aircraft landing gear assembly according toanother embodiment of the invention, with a different type of auxiliaryunlock actuator, when the gear is deployed;

FIG. 8 is a diagram of the landing gear assembly of FIG. 7 showing theauxiliary unlock actuator when the gear is stowed; and

FIG. 9 is a schematic diagram, with the positions of the auxiliaryunlock actuator and abutment reversed as compared to the embodimentshown in FIG. 5.

DETAILED DESCRIPTION

FIG. 1 shows an aircraft landing gear assembly 10 according to anembodiment of the invention. The aircraft landing gear assembly 10 canbe a main landing gear assembly or a nose gear assembly.

The main load bearing strut 12 has a main aircraft pivot bearing 14 at afirst, upper end which is arranged to provide a pivot coupling to theairframe AF of an aircraft. The strut 12 can be moved about the axis ofthe pivot bearing 14 between a stowed condition for flight and adeployed condition for take-off, landing and taxiing.

In this embodiment the strut 12 is a shock absorbing oleo strut havingan upper cylinder 12 a and telescoping sliding tube 12 b. However, inother embodiments the strut can take any suitable form and can forexample comprise a rigid strut.

A second end of the strut 12, in this embodiment a lower end of thesliding tube 12 b when the strut 12 is deployed, is arranged to defineor be coupled to a ground contacting assembly such as a wheel and brakeassembly 16. In this embodiment a lower end of the sliding tube 12 b isarranged to be coupled to the ground contacting assembly. The wheel andbrake assembly can comprise one or more wheel and brake sets mounted onone or more axles. In some embodiments a plurality of axles can bemounted on a bogie beam or other pivoting arm pivotally coupled directlyor indirectly to the second end of the strut. In other embodiments theground contacting assembly can comprise a skid or the like.

The landing gear assembly 10 further comprises a stay 18 arranged tohold the main strut 12 in the deployed condition. The stay 18 comprisesa first stay element 18 a having a first end pivotally coupled to afirst end of a second stay element 18 b to define a stay apex joint 20,a second end of the first stay element 18 a defining a stay pivotbearing 22 via which the stay 18 is arranged to be pivotally coupled tothe airframe AF of the aircraft. A second end of the second stay element18 b defines a second stay pivot bearing 24 which is arranged to bepivotally coupled to a lug 12 c on the outer cylinder 12 a of the strut12 such that the stay 14 can be folded and unfolded between a lockingcondition as shown in FIG. 1, in which the stay inhibits movement of thestrut from the deployed condition to the stowed condition, and a passivecondition in which the stay permits movement of the strut from thedeployed condition to the stowed condition.

In the illustrated embodiment the stay elements 18 a, 18 b are elongate,straight bars having lug pairs at their ends to define the stay pivotbearings 22, 24 and the stay apex joint 20. Thus, each stay element 18a, 18 b has a longitudinal axis L1, L2 extending between the pivot axesat its ends. When in the locking condition, the longitudinal axis L1 ofthe first stay element 18 a is generally aligned with the longitudinalaxis L2 of the first stay element 18 b to place the stay 18 in anover-centre arrangement in which one or more abutments (not shown)prevent further folding of the stay 18 in one direction of rotationabout the apex joint 20. In this condition, the stay 18 reacts axialloads applied to it by the main strut 12 attempting to move from thedeployed condition. When the stay 18 is folded, it does not react axialloads applied to it by the main strut 12 to hold the main strut 12 inthe deployed condition. In other embodiments the stay elements 18 a, 18b can have any suitable form; for example, the stay need not beover-centre when in the locking condition, as a lock link (describedbelow) can hold the stay in a locking condition.

The landing gear assembly 10 further comprises a lock link 26 comprisinga first link element 26 a having a first end pivotally coupled to afirst end of a second link element 26 b to define a lock link apex joint28, and a second end of the first link element 26 a defining a lock linkpivot bearing 30 via which the lock link is arranged to be pivotallycoupled to the strut 12 at a first location which is closer to the firstend of the strut 12 than the second end. The lock link pivot bearing 30can be pivotally coupled to a lug 12 d or other suitable mountingformations which extend from a region of the main strut 12 above themain aircraft pivot bearing 14 towards the stay pivot bearing 22. Asecond end of the second link element 26 b defines a pivot bearing whichis pivotally coupled to the stay apex joint 20. In other embodiments thelock link can have any suitable attachment point to the main strut andstay.

The landing gear assembly 10 has a reinstating geometry. Thus, the locklink 26 is arranged such that it can be folded and unfolded between: afirst locking condition, as shown in FIG. 1, in which the lock link 26inhibits movement of the stay 18 from the locking condition to thepassive condition; a passive condition, as shown in FIGS. 2 and 3, inwhich the lock link 26 permits movement of the stay 18 from the lockingcondition to the passive condition; and a second locking condition, asshown in FIG. 4, in which the lock link 26 inhibits movement of thestrut 12 from the stowed condition towards the deployed condition.

The passive condition lies between the first and second lockingconditions as the strut moves between the deployed condition and stowedcondition.

In the illustrated embodiment the lock link elements 26 a, 26 b areelongate, straight bars having lug pairs at their ends to define thelock link pivot bearings 20, 30 and the lock link apex joint 28. Thus,each lock link element 26 a, 26 b has a longitudinal axis L3, L4extending between the pivot axes at their ends. When in the lockingcondition, the longitudinal axis L3 of the lock link element 26 a isgenerally aligned with the longitudinal axis L4 of the second lock linkstay element 26 b to place the lock link 26 in an over-centrearrangement in which one or more abutments (not shown) prevent furtherfolding of the lock link 26 in one direction of rotation about the apexjoint 28. Springs (not shown) may be employed in a variety of positionsin order to retain the lock links in their locked positions when thegear is deployed or stowed. The lock link 26 reacts axial loads appliedto it by the stay 18 when in the first locking condition. The lock link26 also reacts loads applied to it by the main strut 12 attempting tomove from the stowed condition when in the second locking condition.When the lock link 26 is folded, it does not react axial loads appliedto it. In other embodiments the lock link elements 26 a, 26 b can haveany suitable form.

The landing gear assembly 10 further comprises an unlock actuator 32having a first end pivotally coupled via a first actuator pivot bearing34 to the first stay element 18 a to define a first actuator pivotpoint. A second end of the actuator 32 is pivotally coupled to the locklink 26 via a second actuator pivot bearing 36 to define a secondactuator pivot point. The second actuator pivot bearing 36 is positionedso as to be closer to the lock link apex joint 28 than the second end ofthe second lock link element 26 b in order to provide mechanicaladvantage, but this does not need to be so; for example, the secondactuator pivot bearing 36 can be located on the other side of stay apex20 so the unlock actuator 32 pushes, rather than pulls, to unlock fromthe deployed condition yet still reverses when stowed.

The unlock actuator 32 is operable to change the distance between thefirst actuator pivot bearing 34 and the second actuator pivot bearing 36such that, in this embodiment, the actuator 32 can move the lock link 26from the first locking condition to the passive condition by retracting.This is illustrated in FIG. 2. In embodiments of the invention theretraction actuator 38 can have any suitable configuration, such asbeing coupled at one end to a hard point on the airframe AF and atanother end of a lug 12 e on the main strut 12. In other embodiments,the unlock actuator can be coupled to the first stay element at alocation closer to the stay pivot bearing 22 than the stay apex joint 20and coupled to either link 26 a, 26 b of the lock link 26 such that theunlock actuator also serves as the retraction actuator.

Once the lock link 26 has been unlocked, further unfolding causes thestay 18 to be broken and unfolded to the passive condition. As shown inFIG. 3, a retraction actuator 38 can then move the main strut 12 to thestowed condition, with both the stay 18 and lock link 26 being passivelyarticulated by movement of the main strut 12. Part way through theretraction phase the geometry of the assembly and the load from theretraction actuator will overpower the unlock actuator 32 and force itto reverse direction and extend and for its axis to pass over the centreof the stay apex joint 20. As the main strut 12 approaches the stowedcondition the unlock actuator 32 continues to exert a pulling force andwill now pull the lock link 26 into line and then over-centre, causingthe lock link 26 to assume the second locking condition.

Thus, the landing gear assembly 10 includes an unlock actuator 32 thatis anchored to the upper stay element 18 a. The present inventor hasfound that this results in a reinstating geometry in which the unlockactuator 32 can apply load in one direction only to unlock the lock link26 from the deployed strut condition and then lock it again in thestowed gear condition, thus avoiding the need for sequential controlduring movement of the main strut 12 from one condition to the other.

When the main strut 12 is to be deployed, the unlock actuator 32 canmove the lock link from the second locking condition to the passivecondition by extending.

As shown in FIG. 5, in the illustrated embodiment the landing gearassembly 10 further comprises a linear auxiliary unlock actuator 40 or“kicker” actuator arranged to either supplement, or replace, theunlocking force applied to the lock link 26 by the unlock actuator 32when the lock link 26 is holding the main strut 12 in the stowedcondition; for example if the unlock actuator fails. The auxiliaryunlock actuator 40 is operable to change in length between a firstextension state and a second extension state. The auxiliary unlockactuator 40 is mounted on the first stay element 18 a such that it facesthe lock link 26 when the main strut 12 is stowed, as shown in FIG. 6,such that extension of the auxiliary unlock actuator 40 causes an endeffector, which in this embodiment is a free end E of actuator 40, tomove along an actuation path to come into contact with a contact face onthe lock link 26 to unlock the lock link 26 when the lock link 26 is inthe second locking condition. The contact face can comprise an abutmentformation A provided or mounted on the lock link 26 for contact with thefree end E of the auxiliary unlock actuator 40 when it is operated toextend. It is preferred that the actuation path is generally orthogonalto the contact face, at least the portion of the actuation path that isadjacent to the contact face.

The auxiliary unlock actuator 40 is mounted in a positionally fixedrelationship with respect to the stay element 18 a; for example, by wayof a pair of nut and bolt fixings or any other suitable fixing orbonding arrangement. Advantageously, when the auxiliary unlock actuator40 is located on the upper stay element 18 a and arranged to face thelock link 26 when the main strut 12 is stowed, the geometry of the mainstrut 12, stay 18, and lock link 26, means that the auxiliary unlockactuator 40 will not face the lock link 26 when the strut is in thedeployed condition. This is shown in FIG. 5. Thus, when the lock link 26is in the first locking condition accidental operation of the auxiliaryunlock actuator 40 cannot unlock the lock link 26.

Referring now to FIGS. 7 and 8, in another embodiment the landing gearassembly 50 can be provided with a linear auxiliary unlock actuator 52that is operable to extend or retract to move a pivoting leg 54 pivotedto part of the stay 18 such as the apex joint 20. The actuator 52 ispivotally coupled to the stay 18 via pivot bearing 56 and pivotallycoupled to the leg 54 via pivot bearing 58. As shown in FIG. 8, when thestrut is in the stowed condition the swinging leg 54 is close enough tothe lock link abutment A to unlock the lock link by way of, in thiscase, extension of the auxiliary actuator 52. However, when the strut 12is in the deployed condition, as shown in FIG. 7, extension of theactuator 52 will not cause the leg 54 to contact the abutment A.

In other embodiments the auxiliary unlock actuator can be arranged toact directly on the lock link rather than an abutment on it.

In other embodiments the above-described examples can be reversed suchthat the auxiliary unlock actuator is mounted on the lock link andarranged to contact the stay to break the lock link, such asschematically illustrated in FIG. 9. Such embodiments have an advantagein that the power lines to the unlock actuator and the auxiliary unlockactuator are relatively segregated, thereby reducing the likelihood ofdamage by a common cause. It is preferred that auxiliary unlock actuatoris powered by a different power source, such as a different hydraulicsupply, than the unlock actuator.

In other embodiments the landing gear assembly can have any reinstatinggeometry (i.e. the unlock actuator may not be coupled to the first stayelement 18 a) and be provided with an auxiliary unlock actuator 40 asdescribed above.

In the illustrated embodiment the unlock actuator 32, the auxiliaryunlock actuator 40, and the retraction actuator 38 are all linearactuators, but in other embodiments any suitable actuator type can beprovided.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe capable of designing many alternative embodiments without departingfrom the scope of the invention as defined by the appended claims.

1. An aircraft landing gear assembly comprising: a main load bearingstrut having a first end arranged to be movably coupled to an aircraftfor the strut to be moved between a stowed condition for flight and adeployed condition for take-off and landing, and a second end arrangedto define or be coupled to a ground contacting assembly; a staycomprising a first stay element having a first end pivotally coupled toa first end of a second stay element to define a stay apex joint, asecond end of the first stay element being arranged to be pivotallycoupled to the aircraft and a second end of the second stay elementbeing arranged to be pivotally coupled to the strut such that the staycan be folded and unfolded between: a locking condition in which thestay is arranged to prevent movement of the strut from the deployedcondition to the stowed condition; and a passive condition in which thestay arranged to permit movement of the strut from the deployedcondition to the stowed condition; a lock link comprising a first linkelement having a first end pivotally coupled to a first end of a secondlink element to define a lock link apex joint, a second end of the firstlink element being pivotally coupled to the strut at a first locationwhich is closer to the first end of the strut than the second end, and asecond end of the second link element being coupled to the stay at oradjacent to the stay apex joint such that the lock link can be foldedand unfolded between: a first locking condition in which the lock linkis arranged to prevent movement of the stay from the locking conditionto the passive condition; a passive condition in which the lock link isarranged to permit movement of the stay from the locking condition tothe passive condition; and a second locking condition in which the locklink is arranged to prevent movement of the strut from the stowedcondition towards the deployed condition, the passive condition lyingbetween the first and second locking conditions as the strut movesbetween the deployed condition and stowed condition; and an unlockactuator having a first end pivotally coupled to the first stay elementat a first actuator pivot point and a second end pivotally coupled tothe lock link at a second actuator pivot point such that the actuatorcan move the lock link from the first locking condition to the passivecondition by one of extending or retracting and that the actuator canmove the lock link from the passive condition to the second lockingcondition by the same one of extending or retracting.
 2. An aircraftlanding gear assembly according to claim 1, wherein the landing gearassembly is arranged such that the unlock actuator can move the locklink from the second locking condition to the passive condition by theopposite one of extending or retracting.
 3. An aircraft landing gearassembly according to claim 1, wherein the first end of the unlockactuator is coupled to the first stay element at a location which iscloser to the stay apex joint than the second end of the first stayelement.
 4. An aircraft landing gear assembly according to claim 1,wherein the second end of the unlock actuator is pivotally coupled tothe second link of the lock link.
 5. An aircraft landing gear assemblyaccording to claim 1, further comprising an auxiliary unlock actuatorincluding an end effector and being operable to move the end effectoralong an actuation path between a first extension state and a secondextension state, the auxiliary unlock actuator being either: mounted onthe stay and arranged such that when the lock link is in the secondlocking condition the lock link intersects the actuation path but whenthe lock link is in the first locking condition the lock link does notintersect the actuation path, such that movement of the end effectorfrom the first extension state to the second extension state unlocks thelock link by contacting the lock link when the lock link is in thesecond locking condition, but movement of the end effector from thefirst extension state to the second extension state does not unlock thelock link when the lock link is in the first locking condition; ormounted on the lock link and arranged such that when the lock link is inthe second locking condition the stay intersects the actuation path butwhen the lock link is in the first locking condition the stay does notintersect the actuation path, such that movement of the end effectorfrom the first extension state to the second extension state unlocks thelock link by contacting the stay when the lock link is in the secondlocking condition, but movement of the end effector from the firstextension state to the second extension state does not unlock the locklink when the lock link is in the first locking condition.
 6. Anaircraft landing gear assembly according to claim 5 wherein theauxiliary unlock actuator comprises a linear actuator.
 7. An aircraftlanding gear assembly according to claim 1, further comprising aretraction actuator operable to change in length between a firstextension state and a second extension state, the retraction actuatorbeing coupled to the main strut such that movement of the retractionactuator from the first extension state to the second extension statecauses the main strut to move from the deployed condition to the stowedcondition.
 8. An aircraft landing gear assembly according to claim 7wherein the retraction actuator comprises a linear actuator.
 9. Anaircraft landing gear assembly according to claim 7, wherein theretraction actuator is distinct from the unlock actuator.
 10. Anaircraft landing gear assembly according to claim 1, wherein the unlockactuator comprises a linear actuator.
 11. An aircraft including one ormore aircraft landing gear assemblies, each: aircraft landing gearassembly comprising: a main load bearing strut having a first endarranged to be movably coupled to an aircraft for the strut to be movedbetween a stowed condition for flight and a deployed condition fortake-off and landing, and a second end arranged to define or be coupledto a ground contacting assembly; a stay comprising a first stay elementhaving a first end pivotally coupled to a first end of a second stayelement to define a stay apex joint, a second end of the first stayelement being arranged to be pivotally coupled to the aircraft and asecond end of the second stay element being arranged to be pivotallycoupled to the strut such that the stay can be folded and unfoldedbetween: a locking condition in which the stay is arranged to preventmovement of the strut from the deployed condition to the stowedcondition; and a passive condition in which the stay is arranged topermit movement of the strut from the deployed condition to the stowedcondition; a lock link comprising a first link element having a firstend pivotally coupled to a first end of a second link element to definea lock link apex joint, a second end of the first link element beingpivotally coupled to the strut at a first location which is closer tothe first end of the strut than the second end, and a second end of thesecond link element being coupled to the stay at or adjacent to the stayapex joint such that the lock link can be folded and unfolded between: afirst locking condition in which the lock link is arranged to preventmovement of the stay from the locking condition to the passivecondition; a passive condition in which the lock link is arranged topermit movement of the stay from the locking condition to the passivecondition; and a second locking condition in which the lock link isarranged to prevent movement of the strut from the stowed conditiontowards the deployed condition, the passive condition lying between thefirst and second locking conditions as the strut moves between thedeployed condition and stowed condition; and an unlock actuator having afirst end pivotally coupled to the first stay element at a firstactuator pivot point and a second end pivotally coupled to the lock linkat a second actuator pivot point such that the actuator can move thelock link from the first locking condition to the passive condition byone of extending or retracting and that the actuator can move the locklink from the passive condition to the second locking condition by thesame one of extending or retracting.